The escalating requirements for high-density and performance associated with ultra large scale integration (ULSI) semiconductor devices require responsive changes in interconnection technology. Low dielectric constant (low-k) interlevel dielectric (ILD) materials have been found effective in mitigating RC (resistance capacitance) propagation delays to reduce power consumption and crosstalk. Materials which show promise as low-k ILDs include various carbon-containing materials. Such carbon-containing low-k dielectric materials include various polymers with carbon occupying a position in the backbone of the polymer. Typical of such carbon-containing polymers are benzocyclobutene (BCB), methyl silsesquioxane (MSQ), Flare-R®, Silk®, JSR, Orion, and Black Diamond®. Although materials having a dielectric constant of less than about 3.9 are considered low-k dielectric materials, as integrated circuit devices and interconnect technologies continue to scale smaller, low-k dielectric materials with even lower dielectric constants have become useful, and it is increasingly popular and advantageous to use materials having dielectric constants less than or equal to 3, i.e., k≦3. The challenges posed by the increasingly fragile and higher carbon content of the k≦3 materials impact plasma technology used in the manufacture of semiconductor devices because the Si—CH3, Si—C, and other carbon bonds in the low-k dielectric material are susceptible to be attacked by plasma processing.
Conventional methods often employ a plasma treatment of the low-k dielectric film after it is formed, to improve mechanical properties such as hardness and to reduce susceptibility to subsequent plasma attack. Following the plasma treatment, conventional photoresist patterning is carried out, the low-k dielectric film is etched and the photoresist film removed. The organic photoresist film is conventionally removed in a dry plasma process that uses oxygen. Plasma excitation during the stripping process results in atomic oxygen which oxidizes the organic photoresist into gases such as CO, CO2 and H2O that are easily removed from the stripping chamber by conventional pumping. This stripping process undesirably degrades the low-k dielectric material because the oxygen used in the stripping process also combines with carbon from the low-k dielectric film, disrupts existing carbon bonds, and causes the carbon to leach out of the low-k dielectric film. The loss of carbon undesirably causes the dielectric constant of the film to increase. Another shortcoming of this conventional method is that the post-deposition plasma treatment only treats the top surface of a low-k dielectric film after deposition and does not treat surfaces of the film that become exposed during the subsequent etching process used to form trenches, vias, contacts and other openings in the low-k dielectric material.
It would therefore be desirable to provide a method for manufacturing a semiconductor device that overcomes the above shortcomings and does so in an efficient, streamlined processing sequence.